1. Field of the Invention
The present invention relates generally to a TV lens control apparatus, and more particularly to a control apparatus applied to a TV lens apparatus, which is constructed in such a way as to adjust a flange back focal length by moving a master lens group of a shooting lens optical system by a motor.
2. Description of Related Art
A conventional shooting lens optical system of a TV lens apparatus used for a broadcasting TV camera comprises a focus lens group, a zoom lens group and a master lens group. To properly make an image-forming position of the lens optical system coincide with a position of a picture sensing surface of the camera, the master lens group is moved forward or backward along an optical axis to adjust a flange back focal length (tracking adjustment). The master lens group is moved not only to adjust the flange back focal length but also to get a special effect by intentionally blurring an image while shooting. Normally, the position of the master lens group is adjusted by turning a flange back focal length (F.f.) adjustment knob provided at a lens apparatus body. The master lens group is moved by a motor. There is a TV lens apparatus which enables a macroshooting by moving a master lens group from a F.f. adjusted position (a F.f. position) to a macroshooting position by the operation of a controller, and a TV lens apparatus which enables a shooting with the special effect by moving a master lens group from a F.f. position by the operation of a controller to intentionally shoot a blurred image.
The conventional TV lens apparatus, however, has special controllers for controlling the movements of the lens groups. More specifically, the conventional TV lens apparatus has a focus controller (a focus position demand) for controlling the movement of the focus lens group; a zoom controller (a zoom rate demand) for controlling the movement of the zoom lens group; and a master lens controller for controlling the movement of the master lens group. A cameraman has to operate each controller properly, and thus, it is very complicated to operate the camera.
Japanese Patent Provisional Publication No. 3-109878 discloses a TV lens control apparatus, which drives a master lens group by a motor to enable a macroshooting. According to this TV lens control apparatus, the focus controller is also used to control the master lens group so that the operation of the focus controller can drive the master lens group. This eliminates the necessity of separately operating the focus controller for driving the focus lens and the controller for driving the master lens group. This TV lens control apparatus, however, cannot move the master lens group in order to adjust the flange back focal length although it is able to move the master lens for the macroshooting. More specifically, the master lens group returns to the original F.f. position if the function of the focus controller is switched to the master lens control function to move the master lens group and then the function of the focus controller is switched to the focus lens control function again. It is therefore impossible to adjust the F.f. position by the TV lens control apparatus. If the function of the focus controller is switched from the master lens control function to the focus lens control function, the focus lens group moves to a position designated by a control member (a focus ring) of the focus controller when the master lens is adjusted. Thus, it is necessary to adjust the position of the focus lens group again. On the other hand, if the function of the focus controller is switched from the focus lens control function to the master lens control function, the master lens moves to a position designated by the control member of the focus controller. Thus, it is necessary to adjust the flange back focal length all over again.
In view of the foregoing, it is an object of the present invention to provide a TV lens control apparatus, which makes it easier to operate a TV camera without the necessity of providing a special controller for controlling the movement of a master lens group of a TV lens apparatus.
It is another object of the present invention to provide a TV lens control apparatus, which makes it possible to properly adjust a flange back focal length of a master lens by means of a focus controller or a zoom controller.
To achieve the above-mentioned object, the present invention is directed to a TV lens control apparatus, which drives at least one movable lens of a focus lens and a zoom lens, and a master lens of a TV lens apparatus by motors, said TV lens control apparatus comprising: a controller for designating a position or moving speed of said movable lens and said master lens by operating one control member, said controller outputting a control signal representing a value according to the operation of said control member; selecting means for deciding whether said movable lens or said master lens is the lens subject to be driven by the control signals outputted from said controller; and drive means for moving said lens subject to be driven from a position when said selecting means switches the lens to be driven, in accordance with changes in said control signals outputted from said controller after the switching operation, said drive means keeping the other lens at a position at the switching operation.
According to the present invention, the focus controller for controlling the focus lens and the zoom controller for controlling the zoom lens are used to control a focus lens to thereby adjust the flange back focal length. Moreover, if a lens to be driven by a controller is switched between the focus lens and the master lens or between the zoom lens and the master lens, the lens is moved in accordance with the operation of the controller after the switching regardless of the operation of the controller before the switching. This prevents the master lens from moving to the position designated by the control member of the controller when the lens to be driven by the focus controller is switched to the master lens. In addition, it is possible to adjust the flange back focal length of the master lens from the previously-set F.f. position without adjusting the flange back focal length of the master lens all over again.
To achieve the above-mentioned object, the present invention is directed to a TV lens control apparatus, which has a focus lens group, a zoom lens group and a master lens group and moves each lens group by a motor, said TV lens control apparatus comprising: a focus controller for outputting a lens movement instruction signal in accordance with the operation of a focus control member; a zoom controller for outputting a zoom instruction signal in accordance with the operation of a zoom control member; switch means which is turned on in order to adjust the position of said master lens group; detecting means for detecting the zoom position; and a control part for controlling the drive of said lens groups in accordance with the instruction signals from said focus controller and said zoom controller, said control part using the lens movement instruction signal outputted from said focus controller as a master lens group movement instruction to drive said master lens group in accordance with said lens movement instruction signal if said switch means is turned on and the zoom position detected by said detecting means is at a preset wide-angle side, and using the lens movement instruction signal outputted from said focus controller as a focus lens group movement instruction to drive said focus lens group in accordance with said lens movement instruction signal if the zoom position detected by said detecting means is at a preset telephoto side.
According to the present invention, the focus controller is also used to control the master lens group. Turning on the switch means causes the control part to switch the function of the focus controller from the focus lens group control function to the master lens group control function.
It is possible to blur an image by adjusting the position of the focus lens group since the depth of focus is small at the telephoto side. On the other hand, it is impossible to blur an image by adjusting the position of the focus lens group since the depth of focus is great at the wide-angle side. To address this problem, the image is blurred by adjusting the position of the master lens group. Therefore, according to the present invention, the focus controller controls the movements of the master lens group if the zoom is set at the wide-angle side, and the focus controller controls the focus lens as usual if the zoom is set at the telephoto side.
This eliminates the necessity of providing a special controller for adjusting the position of the master lens group and makes it easier to operate the camera.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.